Hydraulic pump or motor

ABSTRACT

A hydraulic pump or motor of the gear type in which the area between the gears in which the teeth intermesh is connected by a passage in the port plate with the intake and outlet passages of the pump or motor, and a valve directs the flow of fluid entrapped between the teeth of the intermeshing gears preferably to the high pressure side of the pump or motor. The passages containing the valve prevent any appreciable leakage of fluid from the high pressure side to the low side, thus increasing the efficiency of the pump or motor while at the same time preventing any excessive build up of pressure by fluid entrapped between the intermeshing gears.

United States Patent 1191 1111 3,817,665

Myers June 18, 1974 HYDRAULIC PUMP OR MOTOR Primary Examiner-C. J. Husar Assistant ExaminerLeonard Smith [75] Inventor. Bruce B. Myers, South Bend, Ind. Attorney g or Firm Hobbs & Green [73] Assignee: Reliance Electric Company,

Mishawaka, Ind. [57] ABSTRACT 22 Filed; 20 1973 A hydraulic pump or motor of the gear type in which the area between the gears in which the teeth inter- [21] APPL 352,938 mesh is connected by a passage in the port plate with the intake and outlet passages of the pump or motor,

[52 us. c1. 418/189 end a valve direete the flew 9f fluid entrapped [51 lm. c1. F04c 1/04 tween the teeth of the intermeshing gears Preferably [58] Field or Search 418/189, 206 to the high pressure side of the P p or when The passages containing the valve prevent any appreciable 5 References Cited leakage of fluid from the high pressure side to the low UNITED STATES PATENTS side, thus increasing the efficiency of the pump or 1 129 090 2,195 Haw] y 418/189 motor while at the same time preventing any excessive e 2,28l,767 5/1942 Heckert... 418/189 x bi 9 pressure by entrapped between the 2,884,864 5/1959 Bobnar 418/189 x mg gears' 10 Claims,.8 Drawing Figures PATENTEDJun 18 I974 3.817166 5 SHEET 2 BF 4 PATENTEDJum 1914 Y j 3817;665-

sum 3 or 4 HYDRAULIC PUMP OR MOTOR In the conventional gear pumps and motors, the intermeshing gear teeth at the center of the cavity form the barrier to prevent the return of fluid to the inlet passage of the pump, or passage of fluid directly from the inlet passage to the outlet passage of the motor. The intermeshing teeth forming the barrier do not form a complete seal between inlet and outlet passages, and hence fluid escapes between the teeth of the two gears, often sufficient to substantially reduce the efficiency of the pump or motor. Further, during the movement of the teeth between the gears, fluid is trapped in the intermediate area and is forced under high pressure either to the inlet or outlet passages to escape from the closing chambers between the teeth. This leakage or loss of fluid from one passage to the other must necessarily occur in the conventional motor or pump for the device to operate; however, in some motors and pumps this leakage of the entrapped fluid is controlled and relieved by providing porting which permits the entrapped fluid to escape or leak to the low pressure side. While this eliminates the forces normally created in the entrapped fluid, it substantially decreases the efficiency of the device. This leakage condition between the inlet and outlet passages normally increases during the operational life of the device as a result of wear of the teeth from contact between the gears and hence further decreases the efficiency of the device. It is therefore one of the principal objects of the present invention to provide a gear type hydraulic pump or motor which is so constructed that the fluid entrapped between the intermeshing teeth of the gears is automatically returned to the high pressure side of the pump or motor, i.e. to the inlet passage of the motor and the outlet passage of the pump, and which prevents any appreciable leakage of fluid from the high pressure side of the device to the low pressure side, and maintains maximum efficiency of the device over extended periods of operation.

Another object of the invention is to provide a motor or pump of the aforesaid type in which is provided a relatively simple and reliable system for relieving the pressure between the gears by controlling the flow of fluid from the cavities between the contacting teeth, without decreasing the efficiency of the device, and in which the system is incorporated without any appreciable changes in size or design of the basic device.

A further object is to provide, in a gear type hydraulic pump or motor, a system for bleeding the fluid entrapped between the gears using a valve controlled passage communicating with the area between the gears and preferably with the high pressure side of the motor or pump, and which will perform effectively, notwithstanding the occurrence of normal wear of the parts of the parts of the device, particularly the gears, to maintain the device at optimum operating performance.

Additional objects and advantages of the present invention will become apparent from the following description and accompanying drawings, wherein:

FIG. 1 is a side elevational view of a pump or motor embodying the present invention;

FIG. 2 is an end elevational view of the pump or motor shown in FIG. 1;

FIG. 3 is an elevational view of the end opposite that shown in FIG. 2;

FIG. 4 is a vertical cross sectional view of the pump or motor shown in the preceding figures, the section being taken on line 4-4 of FIG. 3;

FIG. 5 is a vertical cross sectional view of the pump or motor shown in the preceding figures, the section being taken on line 55 of FIG. 4;

FIG. 6 is a fragmentary, horizontal cross sectional view of the device shown in the preceding figures, the section being taken on line 66 of FIG. 5;

FIG. 7 is a vertical cross sectional view taken on line 7-7 of FIG. 5; and

FIG. 8 is an enlarged fragmentary sectional view of a portion of the two gears shown in the Circle of FIG. 7.

Referring more specifically to the drawings, numeral 10 indicates generally a hydraulic pump embodying the present invention and having stator 12 and end plates 14 and 16 secured on opposite sides of the stator by a plurality of bolts 18 extending through the three sections. A mounting flange 20 with bolt holes 21 is formed integrally with end plate 16, and is adapted to be mounted on a motor or other source of power. While the description is directed to a hydraulic pump, the device embodying the invention can be used equally satisfactorily as a hydraulic motor.

The stator 12 contains two generally circular cavities 30 and 32 for gears 34 and 36, respectively. Gear 34 is mounted on an idle shaft 37 which is journaled in bearings 38 and 40 disposed in the inner walls of end plates 14 and 16, respectively. The shaft contains a bore 42 which communicates pressure from one side of the gear and shaft to the other side, and between the outer sides of plates 44 and 46 so that these parts will be hydraulically balanced throughout the operation of the pump. Gear 36 is mounted for rotation with a drive shaft 48 which is journaled in bearing 50 disposed in a recess in end plate 14, and in bearing 52 disposed in a bore in end plate 16. The shaft extends outwardly through end plate 16 and flange 20 and has an end 54 for receiving a coupling or other connection for a motor for driving the shaft, and hence the gear mounted thereon which is connected to the shaft by a key 56 in key ways 58 and 60 in the shaft and gear, respectively. The shaft is sealed at the outer end of end plate 16 by seal 62, and any leakage of hydraulic fluid behind port plates 44 and 46 is relieved by passage 64 extending longitudinally throughout most of the length of the shaft and being connected with the bore in end plate 16 by radial passages 66 and 68. A port 70 is provided through end plate 14 for connecting passage 64 with a drain pipe or tube (not shown).

The present pump is designed to operate in either direction; however, for the purpose of the description, pump passage will be considered as the fluid inlet or low pressure side of the pump, and passage 82 the outlet or high pressure side of the pump. Inlet passage 80 is connected to the cavity in the stator by recesses 84 and 86, and with outlet passage 82 by recesses 88 and 90. As gear 36 is driven by shaft 48, fluid is drawn inwardly through passage 80 and recesses 84 and 86, and is carried by the teeth around the periphery of cavities 30 and 32 and is discharged through recesses 88 and 90 into outlet passage 82. The teethintermesh in the area between gears 34 and 36, thus preventing the return of most of the fluid to the inlet side of the pump. However, the intermeshing gears would inherently create a closed chamber or cavity between the gears in the return stage in the area identified by numerals 92 and 92a, and this entrapped fluid therein be at least partially removed therefrom in order to permit satisfactory operation of the gears. This is usually accomplished by facilitating leakage from the fluid trapping area by enlargement of the recesses so that there is momentary communication between recesses 86 and 88, respectively, during the passage of the gears from the outlet side to the inlet side of the pump. This inherently decreases the efficiency of the pump since there is a loss of fluid and pressure in relieving the fluid between the intermeshing gears in this manner.

The present invention overcomes the loss of efficiency normally resulting from leakage from the high pressure side to the low pressure side of the pump by providing a system which returns the fluid entrapped between the gears to the high pressure side of the pump or motor. This is accomplished by providing a port 100 positioned substantially on the center line between the two gears in the area at which the gears intermesh. The port is connected by passages 102 and 103 with passages 80 and 82, and a valve consisting of a ball 104 is disposed in an enlarged chamber 106 between passages 102 and 103. The ball is forced by the high pressure in chamber 106 to seat on the end of and close passage 103, thereby forming direct communication in the area between the teeth in which the fluid is entrapped through port 100, chamber 106 and passage 103 to recess 86, which in turn communicates with inlet passage 80, thus connecting the cavity between the teeth in which the fluid is entrapped with passage 103, recess 90, and outlet passage 82. Since the pressure of the entrapped fluid would normally become substantially greater than the pressure of the outlet of the pump, the flow of fluid from the area takes place with little resistance from the pressure of the fluid on the outlet or high pressure side of the pump and is sufficient to maintain ball valve 104 firmly seated over the end of passage 102. Thus the fluid which normally passes through the conventional pump to the inlet side is directed back through the port 100 in the port plates 44 and 46 to the high pressure side, and therefore is not lost in the operation of the pump. Recesses 84 and 88 are provided with inwardly extending portions 110 and 112 which permit the closing area between the teeth to communicate with the respective side throughout a substantial portion of the intermeshing condition, so that the fluid is automatically returned to the high side until a closed cavity is formed between the teeth at which time port 100 communicates with the entrapped fluid, thereby performing the operation of relieving the pressure by returning the fluid to the high pressure side of the pump.

in the operation of the pump, the shaft 48 is driven by a motor or other suitable source of power, causing rotation of gear 36 which in turn rotates gear 34 and shaft 37, gear 36 being rotated in the counterclockwise direction by shaft 48 and gear 34 in the clockwise direction on shaft 37 as viewed in FIG. 7, thus drawing hydraulic fluid inwardly through passage 80 and recesses 84 and 86. The fluid is carried in the cavities between the teeth around the periphery of pump cavities 30 and 32 to recesses 88 and 90 and is discharged into outlet passage 82. The teeth then intermesh with one another and pass between the gears where the fluid is first expelled from between the gears through recess extension 112. When the fluid becomes entrapped between two of the teeth, the area between the teeth comes in communication with port 100, which drains off the entrapped fluid through passage 103 into recess on the high side of the pump. This permits the gears to move freely without causing any undue stresses on the gear shafts and without encountering any significant loss of the efficiency which normally would occur as a result of leakage from the outlet or high pressure side of the pump to theinlet .orlow pressure side thereof.

The ball valve 104 is adapted to seat on either pas sage 102 or 103 and thereby is adapted to permit the operation of the pump in either direction so that the intake may be passage 82 and the outlet or high pressure side of the pump would be passage 80. The ball valve is readily shifted from seating on the entrance of one passage to the other by the high pressure created by the entrapped fluid, or by that in the high pressure side of the pump. The present pressure relief system of the pump substantially improves the efficiency over the conventional pump and reduces noise and wear which often accompany the entrapment of fluid between the gears. The system functions essentially the same in a motor as in a pump in which the fluid entrapped between the gears is returned to the high pressure side of the device so that the effectiveness of the high pressure fluid is not lost in the operation.

While only one embodiment of the present pump or motor has been described in detail herein, various changes and modifications may be made without departing from the scope of the invention.

I claim: I

1. A hydraulic pump or motor comprising a stator having two interconnecting circular cavities, gears in said cavities having teeth intermeshing in the area between said cavities, plates on each side of said gears, at least one of said plates having a fluid inlet port, at least one of said plates having a fluid outlet port, recesses in at least one of said plates in the area in which the teeth of said gears intermesh communicating with said ports, a port in the proximity of the center of at least one of said plates in the area in which said teeth intermesh communicating with the space between the teeth in which fluid is confined, and a passage connecting said last mentioned port with one of the other of said ports for relieving the pressure of said confined fluid.

2. A hydraulic pump or motor as defined in claim 1 in which a second passage connects said last mentioned port with the other of said first mentioned ports, and in which a pressure responsive valve is included for closing one or the other of said passages.

3. A hydraulic pump or motor as defined in claim 2 in which said valve is responsive to pressure to close the passage connected to the low pressure side of the pump or motor.

4. A hydraulic pump or motor as defined in claim 3 in which a chamber is disposed between said passages and a ball is disposed in said chamber to function as said valve.

5. A hydraulic pump or motor as defined in claim 1 in which one of said gears is mounted on an idle shaft and the other of said gears is mounted on a power shaft projecting from said motor or pump.

6. A hydraulic pump or motor as defined in claim 1 in which said recesses consist of a pair of recesses in each of said circular cavities in the area adjacent said 9. A hydraulic pump or motor as defined in claim 6 in which the recesses in said circular cavity containing the power gear extend inwardly toward one another further than those in the circular cavity having the idler gear.

10. A hydraulic pump or motor as defined in claim 9 in which said last mentioned port is disposed in the area between the recesses in the circular cavity containing the idler gear. 

1. A hydraulic pump or motor comprising a stator having two interconnecting circular cavities, gears in said cavities having teeth intermeshing in the area between said cavities, plates on each side of said gears, at least one of said plates having a fluid inlet port, at least one of said plates having a fluid outlet port, recesses in at least one of said plates in the area in which the teeth of said gears intermesh communicating with said ports, a port in the proximity of the center of at least one of said plates in the area in which said teeth intermesh communicating with the space between the teeth in which fluid is confined, and a passage connecting said last mentioned port with one of the other of said ports for relieving the pressure of said confined fluid.
 2. A hydraulic pump or motor as defined in claim 1 in which a second passage connects said last mentioned port with the other of said first mentioned ports, and in which a pressure responsive valve is included for closing one or the other of said passages.
 3. A hydraulic pump or motor as defined in claim 2 in which said valve is responsive to pressure to close the passage connected to the low pressure side of the pump or motor.
 4. A hydraulic pump or motor as defined in claim 3 in which a chamber is disposed between said passages and a ball is disposed in said chamber to function as said valve.
 5. A hydraulic pump or motor as defined in claim 1 in which one of said gears is mounted on an idle shaft and the other of said gears is mounted on a power shaft projecting from said motor or pump.
 6. A hydraulic pump or motor as defined in claim 1 in which said recesses consist of a pair of recesses in each of said circular cavities in the area adjacent said intermeshing gears and each pair of recesses extend inwardly from said first mentioned ports.
 7. A hydraulic pump or motor as defined in claim 5 in which the recesses in said circular cavity containing the power gear extend inwardly toward one another further than those in the circular cavity having the idler gear.
 8. A hydraulic pump or motor as defined in claim 7 in which said last mentioned port is disposed in the area between the recesses in the circular cavity containing the idler gear.
 9. A hydraulic pump or motor as defined in claim 6 in which the recesses in said circular cavity containing the power gear extend inwardly toward one another further than those in the circular cavity having the idler gear.
 10. A hydraulic pump or motor as defined in claim 9 in which said last mentioned port is disposed in the area between the recesses in the circular cavity containing the idler gear. 